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The Endocrine System
Chapter 13
Endocrinology
• The study of hormones
• Like nervous system- helps control the body
and aid in communication
• Hormone- chemical messenger, travels
through the bloodstream to target cells,
effective at very low concentration
Hormones
• 1) Secreted
– Glands- pituitary,
thyroid, etc.
– Into the bloodstream
Hormones
• 2) Travel through the blood stream to a distant
target
• 3) Exert their effect at very low concentrations
General characteristics
• Some hormones are
produced by small groups
of specialized cells
Hypothalamus
Pituitary gland
• Other hormones are
produced by larger
Parathyroid gland
endocrine glands
• Pituitary gland
• Thyroid gland
• Parathyroid glands
Kidney
• Adrenal glands
• Pancreas
Testis
(in male)
Pineal gland
Thyroid gland
Thymus
Adrenal gland
Pancreas
Ovary
(in female)
Terminating
hormone action
Terminating hormone action
• Degraded in the bloodstream
• Degraded on the receptor
• Endocytosis of receptor-hormone complex
Everyone needs a little regulation…
Regulation of endocrine response
• Governed by negative feedback
• Feedback guided by multiple variables
– Change in physiological variable
– Hormone concentration
Chief cells
HPA axis
• Hypothalamic-Pituitary-Adrenal
• Complex regulation
• Deemed “Master Gland”
• Governs many key endocrine
functions
–
–
–
–
Growth
Blood pressure
Water regulation
Others
Parts of the Pituitary gland
• Posterior pituitary
– Neural tissue
– Secretes neurohormones
• Oxytocin, vasopressin
Parts of the Pituitary gland
• Anterior pituitary
– “True” endocrine gland
– Synthesizes/releases peptide hormones
Anterior Pituitary function
• Hypothalamus (part of the brain) releases
hormones
• Those hormones signal to the anterior
pituitary
• Anterior pituitary releases hormones that
affect peripheral endocrine glands
• Peripheral endocrine glands release hormone
to target cells
–
Hypothalamus
–
Releasing
hormone
(Hormone 1)
+
–
Anterior pituitary
+
Anterior pituitary
hormone
(Hormone 2)
Peripheral endocrine gland
(Hormone 3)
Stimulation
+
Target cells
Inhibition
Trophic hormones
• Trophic hormone- a hormone that controls the
secretion of another hormone
• All end in “tropin”
• http://www.youtube.com/watch?v=WVrlHH1
4q3o
Endocrine pathologies
• Hormone excess, hormone deficiency, or
abnormal responsiveness of target tissue
• Can be primary (last endocrine gland in a
reflex) or secondary (further up, in gland
producing trophic hormone)
Hypersecretion
• Increase in hormone secretion
• Tumors
• Causes dysfunction in
feedback pathway
• Can occur at any point in the
axis
– Hypothalamus
– Pituitary gland
– Adrenal gland
Hypersecretion
• Hypersecretion of GH
• Acromegaly (adult)
– Bones ossified
– Prominent brow
– Reduced testosterone
– Soft tissue swelling
Hypersecretion
• Excess production of GH
• Gigantism (children)
– Exaggerated and prolonged growth in long bones
Hyposecretion
• Dysfunction of the pituitary
• Decreased secretion of GH
• Dwarfism
– Born normal height/weight
– Failure to grow by age 2 yr
Receptor failure
• Plenty of hormone
• Decrease or lack of receptors
Initially thought lack of GH
production, but actually lack of
receptors
Diabetes
• When you eat, food is broken down into
glucose
• Cells use glucose as energy
• The pancreas secretes insulin (hormone),
which helps glucose get into the cells
• Diabetes is a lack of insulin (type 1) or
decreased response of cells to insulin (type 2)
• Glucose can’t get to cells
Type 1
Type 2
Yum…
• http://www.mayoclinic.org/condition/diabete
s/multimedia/blood-sugar/vid-20084642
Signals from nervous
and endocrine systems
Nervous v. Endocrine
Nervous
• Each neuron has a target
cell
Endocrine
• Every cell
Nervous v. Endocrine
Nervous
• Each neuron has a target
cell
• Electrical/chemical
Endocrine
• Every cell
• Chemical (hormones)
Nervous v. Endocrine
Nervous
• Each neuron has a target
cell
• Electrical/chemical
• Fast
Endocrine
• Every cell
• Chemical (hormones)
• Slower
Nervous v. Endocrine
Nervous
• Each neuron has a target
cell
• Electrical/chemical
• Fast
• Short duration
Endocrine
• Every cell
• Chemical (hormones)
• Slower
• Longer lasting
Nervous v. Endocrine
Nervous
• Each neuron has a target
cell
• Electrical/chemical
• Fast
• Short duration
• Intensity control via
frequency
Endocrine
• Every cell
• Chemical (hormones)
• Slower
• Longer lasting
• Intensity control via
quantity